Electromagnetic depth/orientation detection tool and methods thereof

ABSTRACT

Methods and systems for depth and radial orientation detection are provided. Methods for determining the depth or radial orientation of one or more downhole components include the steps of providing a target mass and a using a detection device for detecting the depth and/or orientation of the target mass. In some cases, the target mass is an electromagnet. In certain embodiments, the target mass is a magneto-disruptive element that is detected with a magnetic flux leakage tool. In this way, the target mass acts as a depth or radial orientation marker. Where the target mass is situated downhole in a known radial relationship to another downhole component, the radial orientation of the other downhole component may be deduced once the radial orientation of the target mass is determined. Advantages include higher accuracies and reduced health, safety, and environmental risks.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims benefitunder 35 USC §119(e) to U.S. provisional application Ser. No. 61/505,739filed Jul. 8, 2011, entitled “Electromagnetic Depth/OrientationDetection Tool and Methods Thereof,” which is hereby incorporated byreference.

This application is related to U.S. provisional application Ser. No.61/505,725 titled, “Depth/Orientation Detection Tool and MethodsThereof,” which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to methods and systems for depthand orientation detection tools. More particularly, but not by way oflimitation, embodiments of the present invention include methods andsystems using electromagnetic depth and radial orientation tools forcertain downhole operations, including perforation of downhole conduits.

BACKGROUND

During various downhole operations, it is often desired to determine theradial orientation of one or more components downhole. In theexploration and production of hydrocarbons, conduits often extendconsiderable depths into the subsurface. These substantial subsurfacedistances often complicate determining the orientation of variouscomponents downhole.

One example of a downhole operation that sometimes requires determiningthe radial orientation of one or more downhole components is perforatingdownhole conduits. Perforation is the process by which holes are createdin a casing or liner to achieve efficient communication between thereservoir and the wellbore. The holes thus created from the casing orliner into the reservoir formation allows oil or gas to be produced fromthe formation through the casing or liner to the production tubing. Themost common method of perforation uses a perforating gun equipped withshaped explosive charges.

As might be imagined, it is often desired to perforate a conduit in aradial direction away from certain sensitive downhole components. Forexample, some wells include cables running along the length of theconduit or tubing for transmitting power, real-time data, and/or controlsignals to or from surface equipment and downhole devices such astransducers and control valves. To avoid damaging the cables duringperforation operations, it is necessary to perforate conduit in a radialdirection substantially away from the cable. Other sensitive devices orapparatus may be installed on or in proximity to a conduit to beperforated. In such instances, it is naturally desired to avoid damagingthe sensitive devices due to perforating in the direction of a cable orother sensitive device. In some instances, it is desired to perforateconduit away from the radial direction of another adjacent conduit.

Other applications which benefit from determination of the radialorientation include, but are not limited to, certain treatmentoperations and logging operations. Accordingly, determining the radialorientation of one or more downhole components is advantageous in manyscenarios.

Many conventional devices have been proposed to determine the radialorientation of downhole components but each of these conventional toolssuffer from a variety of disadvantages.

One example of a conventional tool is the magnetic mass tool. Thisapproach requires installation of an additional magnetic mass in theform of a cable laid next to capillary lines to provide magneticsusceptible mass sufficient to be logged by a rotating electromagneticlogging tool. The currently used electromagnetic tools and proceduresare not robust and suffer from poor accuracy, which often lead toundesirably perforating sensitive external components. In addition topoor accuracy, these devices suffer from tensile loading limitations,the need to take time-consuming stationary readings, magneticsusceptible mass requirements among other limitations. These magneticmass tools also require good centralization within the conduit sinceminimal changes in distance can profoundly affect readings of the tool.Poor centralization of the tool often yields false positives resultingin perforation of a conduit in an unintended orientation.

Another conventional approach is to install perforation guns on theoutside of the conduit to be perforated before the conduit is installeddownhole. This alternate configuration undesirably requires a largerborehole to accommodate the perforation gun. Moreover, failure of theperforation gun in this scenario is much more significant as no readysolution is available to address this failure mode.

Other conventional tools require the use of radioactive markers orinjecting the cable with a radioactive fluid. The use of radioactivemarkers and fluids present significant health, safety, and environmentalconcerns. Radioactive materials pose safety and health risks,particularly on the surface before installation downhole. Suchradioactive materials typically require onerous permitting, logistics,and other significant regulatory hurdles to be met. Additionally,disposal of radioactive materials presents other challenges in additionto high costs. Accordingly, using radioactive materials and fluids abovesurface involves many disadvantages.

Accordingly, there is a need for enhanced radial orientation detectiondevices and methods for detecting radial orientations of one or morecomponents downhole and/or perforating conduits downhole that addressone or more of the disadvantages of the prior art.

SUMMARY

The present invention relates generally to methods and systems for depthand orientation detection tools. More particularly, but not by way oflimitation, embodiments of the present invention include methods andsystems using electromagnetic depth and radial orientation tools forcertain downhole operations, including perforation of downhole conduits.

One example of a method for perforating a conduit disposed in asubterranean formation comprises the steps of: providing an inactivatedelectromagnet; wherein the conduit is characterized by a longitudinalaxis and a radial axis; locating the inactivated electromagnet inproximity to the conduit wherein the inactivated electromagnet elementis situated at a radial offset angle from a sensitive apparatus, whereinthe radial offset angle is an angle from about 0° to about 360°;activating the inactivated electromagnet to form an activatedelectromagnet element; detecting the radial location of the activatedelectromagnet; determining a perforation target based on the radiallocation of the activated electromagnet and the radial offset angle soas to reduce the risk of damage to the sensitive apparatus; andperforating the conduit at the perforation target in a directionsubstantially away from the sensitive apparatus so as to not damage thesensitive apparatus.

One example of a method for perforating a conduit disposed in asubterranean formation comprises the steps of: providing a target masshaving a magneto-disruptive element therein; wherein the conduit ischaracterized by a longitudinal axis and a radial axis; locating thetarget mass in proximity to the conduit wherein the target mass issituated at a radial offset angle from a sensitive apparatus, whereinthe radial offset angle is an angle from about 0° to about 360°;detecting the radial location of the magneto-disruptive element with amagnetic flux leakage tool; determining a perforation target based onthe radial location of magneto-disruptive element and the radial offsetangle so as to reduce the risk of damage to the sensitive apparatus; andperforating the conduit at the perforation target in a directionsubstantially away from the sensitive apparatus so as to not damage thesensitive apparatus.

One example of a method for measuring deformation of a subterraneanformation comprises the steps of: (a) providing a plurality of targetmasses at a plurality of depths in the subterranean formation, whereinthe target masses are inactivated electromagnets; (b) activating eachinactivated electromagnet to form activated electromagnet elements; (c)detecting an initial depth of each activated electromagnet to determinea baseline reference depth of each activated electromagnet; (d) allowingthe subterranean formation to deform; (e) after step (d), detecting ameasured depth of each activated electromagnet to determine a subsequentlocation of each activated electromagnet; and (f) comparing the baselinereference depths to the subsequent locations to determine a deformationof the subterranean formation.

One example of a method for determining a radial orientation of asensitive apparatus disposed in a subterranean formation comprises thesteps of: providing an inactivated electromagnet in proximity to aconduit, wherein the conduit is characterized by a longitudinal axis anda radial axis; locating the inactivated electromagnet at a radial offsetangle from the sensitive apparatus, wherein the radial offset angle isan angle from about 0° to about 360°; activating the inactivatedelectromagnet to form an activated electromagnet element; detecting theradial location of the activated electromagnet using a magnetic fluxmeasurement device; and determining a radial location of the sensitiveapparatus based on the radial location of the activated electromagnetand the radial offset angle.

One example of a method for determining a radial orientation of asensitive apparatus disposed in a subterranean formation comprises thesteps of: providing a target mass having a magneto-disruptive elementtherein in proximity to a conduit disposed in the subterraneanformation, wherein the conduit is characterized by a longitudinal axisand a radial axis; locating the target mass at a radial offset anglefrom the sensitive apparatus, wherein the radial offset angle is anangle from about 0° to about 360°; detecting the radial location of themagneto-disruptive element with a magnetic flux leakage tool; anddetermining a radial location of the sensitive apparatus based on theradial location of the magneto-disruptive element and the radial offsetangle.

The features and advantages of the present invention will be apparent tothose skilled in the art. While numerous changes may be made by thoseskilled in the art, such changes are within the spirit of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present disclosure and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying figures, wherein:

FIG. 1 illustrates an example of a radial orientation detection devicedisposed in a wellbore in a subterranean formation in accordance withone embodiment of the present invention.

FIG. 2 illustrates a cross-sectional aerial view of a wellbore withseveral target masses and sensitive devices disposed thereon inaccordance with one embodiment of the present invention.

FIG. 3 illustrates a cross-sectional view of a detection device disposedin a wellbore in a subterranean formation for measuring depth and/orformation deformation in accordance with one embodiment of the presentinvention.

While the present invention is susceptible to various modifications andalternative forms, specific exemplary embodiments thereof have beenshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

The present invention relates generally to methods and systems for depthand orientation detection tools. More particularly, but not by way oflimitation, embodiments of the present invention include methods andsystems using electromagnetic depth and radial orientation tools forcertain downhole operations, including perforation of downhole conduits.

In certain embodiments, methods for determining the radial orientationof one or more downhole components comprise the steps of providing asubstantially nonradioactive target mass, installing the target massdownhole, irradiating the substantially nonradioactive target mass toform a relatively short-lived radioactive target mass which may then bedetected with a radiation detector. In this way, the target mass may actas a radial orientation marker, indicating the radial orientation of thetarget mass. Where the target mass is situated downhole in a knownradial relationship to another downhole component, the radialorientation of the other downhole component may be deduced once theradial orientation of the target mass is determined.

Knowing the radial orientation of a particular downhole component may beuseful in a variety of downhole operations, including, but not limitedto perforation operations. For example, where it is desired to avoiddamaging a sensitive downhole device such as a cable, it is useful to beable to determine the radial orientation of the sensitive apparatus toavoid damaging it during perforation operations. Other optionalvariations and enhancements are described further below.

Advantages of such depth or radial orientation detection methods anddevices include, but are not limited to, higher accuracies, reducedhealth, safety, and environmental risks due to avoiding handling andlogistics of radioactive materials above surface, and reduced complexityas compared to conventional methods.

Reference will now be made in detail to embodiments of the invention,one or more examples of which are illustrated in the accompanyingdrawings. Each example is provided by way of explanation of theinvention, not as a limitation of the invention. It will be apparent tothose skilled in the art that various modifications and variations canbe made in the present invention without departing from the scope orspirit of the invention. For instance, features illustrated or describedas part of one embodiment can be used on another embodiment to yield astill further embodiment. Thus, it is intended that the presentinvention cover such modifications and variations that come within thescope of the invention.

FIG. 1 illustrates a cross-sectional view a wellbore intersecting asubterranean formation. Casing 115 is cemented in borehole 112 throughsubterranean formation 105. Production tubing 117 is nested withincasing 115.

After completion of the wellbore, one or more conduits need to beperforated to allow communication of formation fluids into productiontubing 117 to allow hydrocarbons to be produced to surface 110. As shownhere in FIG. 1, both production tubing 117 and casing 115 need to beperforated to allow formation fluids into production tubing 117. In someembodiments, however, production tubing terminates at some point abovethe interval to be produced. In these embodiments, only casing 115 wouldneed to be perforated as the terminal open end of production tubing 117would permit flow into production tubing 117 without perforatingproduction tubing 117.

Perforation operations downhole must take into account the presence ofany sensitive devices downhole in proximity to the conduits to avoiddamaging the sensitive devices. The term “sensitive apparatus ordevice,” as used herein, refers to any downhole component to which it isdesired to avoid damage. Here, sensitive device 140A is attached tocasing 115, and sensitive device 140B, in this case, a cable, isattached to production tubing 117 opposite to sensitive device 140B. Itis recognized that the sensitive devices may be situated anywhere in thenear wellbore region, including, but not limited to, being attached tocasing 115 or production tubing 117.

For convenience of reference, the axis parallel to the conduits isreferred to herein as a “longitudinal axis.” The term “radial axis,” asused herein, refers to the axis normal to the longitudinal axis andnormal to the surface of the conduits. Stated another way, the radialaxis is parallel to any plane that is normal to the longitudinal axis.Recognizing that over long distances, the direction of the conduits maychange as a function of depth in subterranean formation 105, the termslongitudinal axis and radial axis refer to the orientation of the axislocal to the region of interest. In FIG. 1, the longitudinal axis islabeled the “z” axis, whereas the radial axis is labeled the “x” axis.

Before perforating either conduit (e.g. casing 115 or production tubing117), it is desired to determine the radial orientation of sensitivedevice 140A or 140B to avoid damaging either device 140A or 140B. Radialorientation detection device 130 is run down through borehole 112 todetermine the radial orientation of one or more downhole components, inthis case, sensitive device 140A, sensitive device 140B, or both. Radialorientation detection device 130 works in conjunction with one or moretarget masses, in this case, target mass 150A, target mass 150B, orboth. As will be explained in more detail, radial orientation detectiondevice 130 is adapted to determine the radial orientation of a targetmass. Since the spatial relationship between the target mass and itscorresponding sensitive apparatus is known, the radial orientation ofthe sensitive apparatus can be determined once the radial orientation ofthe target mass is determined. In this way, by determining the radialorientation of one of the target masses, the radial orientation of anycorresponding sensitive apparatus may be deduced.

In some configurations, a target mass may be situated directly adjacentto a sensitive device. As shown in FIG. 1, target mass 150A is situateddirectly adjacent to sensitive device 140A. Target mass 150B is situatedin the same radial orientation as sensitive device 140B. In certainembodiments, the target mass may be integral to the sensitive device. Insome embodiments, it may be preferred to clamp the target mass to thesensitive device. It is also recognized that a target mass may belocated in any spatial relationship to its corresponding sensitivedevice by any radial offset angle.

FIG. 2 shows an aerial cross-section view, illustrating these concepts.Production tubing 117 is nested within casing 115. Sensitive devices140A and 140C are attached to casing 115, and sensitive device 140B isattached to production tubing 117. Target masses 150A and 150B are alsoattached to casing 115. The term, “radial offset angle,” as used herein,refers to the radial angle between a target mass and its correspondingsensitive device. By knowing the radial offset angle between a targetmass and a sensitive device, the radial orientation of the sensitivedevice may be deduced once the radial orientation of the correspondingtarget mass is determined. As an example of a target mass offset from asensitive device, target mass 150A is situated at a radial offset angle(θ) of about 110° from sensitive device 140C. Target mass 150A issituated at a radial offset angle of about 180° from sensitive device140B, whereas target mass 150B is situated at a radial offset angle ofabout 180° from sensitive device 140A. It is recognized that a targetmass may be situated at any radial spatial relationship relative to itscorresponding sensitive device, that is, any angle between 0° and 360°.

Although the example depicted in FIG. 2 contemplates three targetmasses, it is recognized that any number of target masses may be used,including simply using a single target mass to locate one or moresensitive devices.

Upon determining the position of the target mass together with knowledgeof the spatial relationship between the target mass and itscorresponding sensitive device, a perforation target may be determined.The perforation target refers to any radial orientation away from thesensitive device that, when perforated, avoids damage to the sensitivedevice. The perforation target may be a single radial orientation or arange of safe perforation angles, as desired. Often, a perforationtarget will be chosen that is situated about 180° from the sensitivedevice to minimize damage to the sensitive device. Examples of suitableperforation targets include, but are not limited to, angles of about170° to about 190° from the sensitive device. In certain embodiments,the target mass is located at the preferred perforation target or in thesame radial orientation as the preferred perforation target.

Radial orientation detection device 130 may use a number of mechanismsto determine the radial orientation of a target mass. In certainembodiments, radial orientation detection device 130 comprisesirradiation module 132 and radiation detection module 134. Initially,target masses 150A and 150B are substantially nonradioactive so as tonot pose a safety, health, or environmental threat when being handledabove surface. The initial nonradioactivity of target masses 140A and140B significantly eases the permitting, logistics, and handling oftarget masses 140A and 140B.

When the target masses are established downhole, safely away from thesurface and personnel, irradiation module may expose the region inproximity to the target masses to convert the substantiallynonradioactive target masses into temporarily radioactive target masses.

Irradiation module 132 may use any type of radiation sufficient toconvert substantially nonradioactive target masses into temporarilyradioactive target masses. Examples of suitable ionizing radiationinclude, but are not limited to, gamma radiation, neutron radiation,proton radiation, UV radiation, X-ray radiation, or any combinationthereof. Examples of suitable ionizing radiation modules include, butare not limited to, a high flux neutron generator source (e.g.acceleration of deuterium onto a tritium target source), a chemicalneutron source, a high energy X-ray tub, chemical gamma ray sources(e.g. cesium, cobalt 60, etc), or any combination thereof. Examples ofsuitable high-flux neutron sources include, but are not limited to,plutonium-beryllium, americium-beryllium, americium-lithium, anaccelerator-based neutron generator, or any combination thereof. As usedherein, the term “high-flux neutron source,” refers to any neutrongenerator or chemical neutron source, generally producing about 10,000or more neutrons per second (e.g. present commercial minitrons forlogging produce approximately 4*10̂8 neutrons per second). In response tothe desire to move away from chemical source neutron tools, some modernneutron tools have been equipped with electronic neutron sources, orneutron generators (e.g. minitrons). Neutron generators contain compactlinear accelerators and produce neutrons by fusing hydrogen isotopestogether. The fusion occurs in these devices by accelerating eitherdeuterium (²H=D) or tritium (³H=T), or a mixture of these two isotopes,into a metal hydride target, which also contains either deuterium (²H)or tritium (³H), or a mixture of these two isotopes. In about 50% of thecases, fusion of deuterium nuclei (d+D) results in the formation of a³He ion and a neutron with a kinetic energy of approximately 2.4 MeV.Fusion of a deuterium and a tritium atom (d+T) results in the formationof a ⁴He ion and a neutron with a kinetic energy of approximately 14.1MeV.

The target mass may comprise any material that, when exposed to ionizingradiation, becomes radioactive for a relatively short half life.Examples of suitable materials include, but are not limited to,materials, which when exposed to ionizing radiation, produce radioactivematerials having relatively short half-lives of less than about 32 days,less than about 8 days, less than about 3 days, less than about 30seconds, or less than about 1 second. One advantage of using targetmasses with relatively short half-lives is that the target masses remainradioactive for only a relatively short period of time, reducingpossible radiation exposure risks. Thus, if the target mass needs to beremoved from the well bore and handled above surface for example, anyhealth and safety exposure issues can be avoided. Examples of suitablematerials for target masses include, but are not limited to, tin,molybdenum, gallium, scandium, chlorine, rhodium, cadmium, cesium,tellurium, iodine, xenon, gold, water, oxygen, or any combinationthereof. Additionally, salts or compounds of any of the foregoingmaterials may be used as desired.

Upon forming a temporarily radioactive target mass, the radioactivetarget mass may then be detected. In this example, radiation detectionmodule 134 detects and determines the radial orientation of nowradioactive target mass 150A or 150B. Radiation detection module 134 maycomprise any detection device capable of detecting radioactive responsesfrom a radioactive target mass, including, but not limited to, an x-raydetector, a gamma ray detector, a neutron detector, and a proportionaldetector (e.g. proportional to the energy of the particle detected).These detectors may comprise various components shielded to measure incertain radial directions, or shielded with an open window and rotatedabout the axis of the logging tool. In either case, a reference toradial angle versus a reference must be known. In the case of the use ofmulti-detectors, the tools geometry is known to a reference within thetool. In the case of rotating a single windowed detector, the radialdirection of the detector window is recorded and known at all times. Async or reference may be included to indicate orientation as the devicerotates. This reference may include reference to a gravity vector, orbased on rotation (such as generating a pulse or pulses each time thetool rotates past a known position on the non-rotating portion of thetool. In certain embodiments, radiation detection module 134 comprisesan x-ray backscatter spectrometer.

Upon determining the radial orientation of one of the radioactive targetmasses (e.g. 150A), the radial orientation of one of the sensitivedevices (e.g. 140A or 140B) may be deduced since the radial offsetangles between the radioactive target mass 150A and the sensitivedevices 140A and 140B are known. Here, for example, the radial offsetangle between 150A and 140A is about 10°, whereas the radial offsetangle between 150A and 140B is about 180°. In this way, the radialorientation of either sensitive device 140A or 140B may be determined.

Upon knowing the location of one or more sensitive devices, aperforation target may be selected in a direction oriented substantiallyaway from the sensitive devices. In certain embodiments, the perforationtarget is an angle or zone of angles about 180° from the sensitivedevice or from about 170° to about 190° from the sensitive device. Incertain embodiments, the perforation target is chosen as any radialorientation that avoids or minimizes substantial risk of damage to thesensitive device.

Although irradiation module 132, radiation detection module 134, andperforation gun 136 are shown in FIG. 1 as combined into one integraldevice, it is recognized that one or more of these modules may be formedinto separate, stand-alone devices and may be configured in any order tomake an assembly.

In certain embodiments, a target mass may comprises a material that issubstantially radioactively inert. Examples of suitable target massmaterials include, but are not limited to, boron, boronated compounds,gadolinium, cadmium, salts of any of the foregoing, or any combinationthereof. Where the target mass is selected from a material that issubstantially radioactively inert, such as boron, radiation detectionmodule 134 may detect the target mass as any area or region of reducedradioactive response. Normally, most materials become radioactive uponneutron irradiation or bombardment. Boron and boronated compounds, onthe other hand, are unusual compared to most other materials in thatthey are substantially radioactively inert. Thus, in the case of boronand most boronated compounds, what is detected by logging tools is ahigh neutron absorption the usually produced higher gamma ray counts.Typically, return gamma counts decrease substantially, rather thanincreasing as is more normal with most elements. The boron absorbs theneutrons and emits alpha particles to release energy and stabilize thenuclide. Because alpha particles only travel micro-meters in theformation, they are not detected by logging tools.

In this way, substantially non-radioactive target masses may be locatedand their radial orientation determined. Accordingly, the radialorientation of any sensitive devices with known spatial relationships tothe target mass may then be deduced. Again, by using substantiallyradioactively inert target masses, the safety, health, and environmentalexposure risks associated with radioactive target masses may be avoided.

In certain embodiments, the target mass may comprise an electromagnet.In certain embodiments, the electromagnet may comprise a solenoid havinga ferromagnetic core. The target mass may be left in its inactivatedstate until it is desired to locate the target mass. In one example,once detection of the target mass is desired, the electromagnet may beactivated. Upon activation, a radial orientation detection module maydetect the presence and radial orientation of the target mass by themagnetic field resulting from the electromagnet activation. Where thetarget mass is an electromagnet, the radial orientation detection modulemay comprise a device such as the Baker Vertilog or other magnetic fluxmeasurement devices.

The electromagnet may be battery powered, powered from a power cablefrom the surface, induction powered, or any combination thereof. In thisway, problems that would normally occur with using permanent magnets,such as the undesired accumulation of metallic debris around the magnet,are avoided. The undesirable attraction of debris that would naturallyaccumulate around magnets could impede production flow or causeinterference with logging measurements.

In certain embodiments, the target mass comprises a magneto-disruptiveelement. The term, “magneto-disruptive element,” as used herein, refersto any element that produces a recognizable or distinguishable magneticflux signature. Examples of suitable magneto-disruptive elementsinclude, but are not limited to, certain non-uniformities in metalelements such as gouges, scratches, and other non-uniform flaws. Amagneto-disruptive element has a distinguishable magnetic flux signaturewhen its magnetic flux signature is distinguishable from the backgroundmagnetic flux responses of the components in proximity to the targetmass.

Where magneto-disruptive elements are used as the target mass, theradial orientation detection device may comprise a magnetic flux leakagetool, such as the Schlumberger PAL, the EM Pipe Scanner, or the BakerVertilog, or any combination thereof.

In addition to using target masses to detect the radial orientation ofone or more target masses, target masses may be used as a depthmeasuring device. FIG. 3 shows a cross-sectional view illustrating thisconcept. Casing 315 is completed in wellbore 312, which intersectssubterranean formation 305. Target mass 150λ has been preinstalled on orin proximity to casing 315 at a depth that is desired to be measured atsome later time. Where it is desired to measure the depth of target mass150λ, the target masses may comprise any of the previously-describedtypes of target masses, including, but not limited to, non-radioactivetarget masses, short-lived radioactive target masses, substantiallyradioactively inert target masses, electromagnet target masses,magneto-disruptive element target masses, or any combination thereof.Detection device 330 may run along casing 315 using wireline 329 todetect the depth of target mass 350λ. Detection device 330 may comprisea detection module that corresponds to any of the various types oftarget masses described herein including, but not limited to, x-raydetectors, gamma ray detectors, neutron detectors, magnetic fluxdetectors, or any combination thereof. In this way, detection device 330detects the depth of target mass 330.

The depth measuring concept may be extended to measure deformation of asubterranean formation. FIG. 3 also illustrates this concept. Bysituating a plurality of target masses at a series of depths throughouta subterranean formation (e.g. 350A, 350B, 350C, 350D, 350E, and 350F),one may establish an initial baseline reference depth of each targetmass. At a later date, when desired, subsequent locations of each targetmass may be determined. By comparing the initial baseline referencedepths of the target masses to the subsequent locations of the targetmasses, a deformation (e.g. a compression or subsidence) of theformation may be determined.

It is recognized that any of the various types of target masses (e.g.short-lived radioactive target masses, substantially radioactively inerttarget masses, electromagnet target masses, magneto-disruptive elementtarget masses, or any combination thereof) and their correspondingdetection module devices may be used with any of the methods describedherein (e.g. radial orientation determination, depth determination, andformation deformation detection, etc).

It is recognized that any of the elements and features of each of thedevices described herein are capable of use with any of the otherdevices described herein without limitation. Furthermore, it isrecognized that the steps of the methods herein may be performed in anyorder except unless explicitly stated otherwise or inherently requiredotherwise by the particular method.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations and equivalents are considered withinthe scope and spirit of the present invention. Also, the terms in theclaims have their plain, ordinary meaning unless otherwise explicitlyand clearly defined by the patentee.

1. A method for perforating a conduit disposed in a subterraneanformation comprising the steps of: providing an inactivatedelectromagnet; wherein the conduit is characterized by a longitudinalaxis and a radial axis; locating the inactivated electromagnet inproximity to the conduit wherein the inactivated electromagnet elementis situated at a radial offset angle from a sensitive apparatus, whereinthe radial offset angle is an angle from about 0° to about 360°;activating the inactivated electromagnet to form an activatedelectromagnet element; detecting the radial location of the activatedelectromagnet; determining a perforation target based on the radiallocation of the activated electromagnet and the radial offset angle soas to reduce the risk of damage to the sensitive apparatus; andperforating the conduit at the perforation target in a directionsubstantially away from the sensitive apparatus so as to not damage thesensitive apparatus.
 2. The method of claim 1 wherein the activatedelectromagnet comprises a solenoid having a ferromagnetic core.
 3. Themethod of claim 1 further comprising the step of deactivating theactivated electromagnet after the step of detecting the radial locationof the activated electromagnet.
 4. The method of claim 1 furthercomprising the step of attaching the sensitive apparatus to the conduitand wherein the step of locating the target mass further comprisesclamping the target mass to the sensitive apparatus.
 5. The method ofclaim 1 wherein the radial offset angle is about 0° or about 180°. 6.The method of claim 1 wherein the perforation target is radiallysituated about 180° from the sensitive apparatus.
 7. The method of claim1 wherein the perforation target is about 170° to about 190° from thesensitive apparatus.
 8. The method of claim 1 wherein the sensitiveapparatus is a cable adjacent to the conduit and wherein the radialoffset angle is about 0°.
 9. A method for perforating a conduit disposedin a subterranean formation comprising the steps of: providing a targetmass having a magneto-disruptive element therein; wherein the conduit ischaracterized by a longitudinal axis and a radial axis; locating thetarget mass in proximity to the conduit wherein the target mass issituated at a radial offset angle from a sensitive apparatus, whereinthe radial offset angle is an angle from about 0° to about 360°;detecting the radial location of the magneto-disruptive element with amagnetic flux leakage tool; determining a perforation target based onthe radial location of magneto-disruptive element and the radial offsetangle so as to reduce the risk of damage to the sensitive apparatus; andperforating the conduit at the perforation target in a directionsubstantially away from the sensitive apparatus so as to not damage thesensitive apparatus.
 10. The method of claim 9 further comprising thestep of attaching the sensitive apparatus to the conduit and wherein thestep of locating the target mass further comprises clamping the targetmass to the sensitive apparatus.
 11. The method of claim 9 wherein theradial offset angle is about 0° or about 180°.
 12. The method of claim 9wherein the perforation target is radially situated about 180° from thesensitive apparatus.
 13. The method of claim 9 wherein the perforationtarget is about 170° to about 190° from the sensitive apparatus.
 14. Themethod of claim 9 wherein the sensitive apparatus is a cable adjacent tothe conduit and wherein the radial offset angle is about 0°.
 15. Amethod for measuring deformation of a subterranean formation comprisingthe steps of: (a) providing a plurality of target masses at a pluralityof depths in the subterranean formation, wherein the target masses areinactivated electromagnets; (b) activating each inactivatedelectromagnet to form activated electromagnet elements; (c) detecting aninitial depth of each activated electromagnet to determine a baselinereference depth of each activated electromagnet; (d) allowing thesubterranean formation to deform; (e) after step (d), detecting ameasured depth of each activated electromagnet to determine a subsequentlocation of each activated electromagnet; and (f) comparing the baselinereference depths to the subsequent locations to determine a deformationof the subterranean formation.
 16. The method of claim 15 furthercomprising the step of attaching the sensitive apparatus to the conduitand wherein the step of locating the target mass further comprisesclamping the target mass to the sensitive apparatus.
 17. The method ofclaim 15 wherein the radial offset angle is about 0° or about 180°. 18.The method of claim 15 wherein the perforation target is radiallysituated about 180° from the sensitive apparatus.
 19. The method ofclaim 15 wherein the perforation target is about 170° to about 190° fromthe sensitive apparatus. The method of claim 15 wherein the sensitiveapparatus is a cable adjacent to the conduit and wherein the radialoffset angle is about 0°.
 20. A method for determining a radialorientation of a sensitive apparatus disposed in a subterraneanformation comprising the steps of: providing an inactivatedelectromagnet in proximity to a conduit, wherein the conduit ischaracterized by a longitudinal axis and a radial axis; locating theinactivated electromagnet at a radial offset angle from the sensitiveapparatus, wherein the radial offset angle is an angle from about 0° toabout 360°; activating the inactivated electromagnet to form anactivated electromagnet element; detecting the radial location of theactivated electromagnet using a magnetic flux measurement device; anddetermining a radial location of the sensitive apparatus based on theradial location of the activated electromagnet and the radial offsetangle.
 21. The method of claim 20 further comprising the step ofattaching the sensitive apparatus to the conduit and wherein the step oflocating the target mass further comprises clamping the target mass tothe sensitive apparatus.
 22. The method of claim 20 wherein the radialoffset angle is about 0° or about 180°.
 23. The method of claim 20wherein the perforation target is radially situated about 180° from thesensitive apparatus.
 24. The method of claim 20 wherein the perforationtarget is about 170° to about 190° from the sensitive apparatus. Themethod of claim 20 wherein the sensitive apparatus is a cable adjacentto the conduit and wherein the radial offset angle is about 0°.
 25. Amethod for determining a radial orientation of a sensitive apparatusdisposed in a subterranean formation comprising the steps of: providinga target mass having a magneto-disruptive element therein in proximityto a conduit disposed in the subterranean formation, wherein the conduitis characterized by a longitudinal axis and a radial axis; locating thetarget mass at a radial offset angle from the sensitive apparatus,wherein the radial offset angle is an angle from about 0° to about 360°;detecting the radial location of the magneto-disruptive element with amagnetic flux leakage tool; and determining a radial location of thesensitive apparatus based on the radial location of themagneto-disruptive element and the radial offset angle.
 26. The methodof claim 25 further comprising the step of attaching the sensitiveapparatus to the conduit and wherein the step of locating the targetmass further comprises clamping the target mass to the sensitiveapparatus.
 27. The method of claim 25 wherein the radial offset angle isabout 0° or about 180°.
 28. The method of claim 25 wherein theperforation target is radially situated about 180° from the sensitiveapparatus.
 29. The method of claim 25 wherein the perforation target isabout 170° to about 190° from the sensitive apparatus.
 30. The method ofclaim 25 wherein the sensitive apparatus is a cable adjacent to theconduit and wherein the radial offset angle is about 0°.